從PaintComponent中訪問對象方法

Question

我有一些編程經驗，但是面向對象編程和Java是新手。我在調用不同類的類方法時遇到問題。更具體地說，我想從myDrawPanel（board.drawBoard）中的Paintcomponent調用該方法。編譯器告訴我，編譯類mypanel時，符號'board'不被識別。任何建議/信息大加讚賞：代碼如下：

import javax.swing.* ; 
import java.awt.* ; 
import java.awt.event.* ; 
import java.awt.Graphics; 

public class Connect { 

    public static PBoard board = new PBoard() ; 

    public void main(String[] args) { 

     Connect gui = new Connect() ; 
     gui.go() ; 
    } 

    public void go() { 

     JFrame frame = new JFrame() ; 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ; 

     MyDrawPanel drawPanel = new MyDrawPanel() ; 

     frame.getContentPane().add(BorderLayout.CENTER, drawPanel) ; 

     frame.setSize(800,800) ; 
     frame.setVisible(true) ; 

     } 
    } 

import java.awt.* ; 
import javax.swing.* ; 

public class MyDrawPanel extends JPanel { 

    public void paintComponent(Graphics g) { 

    board.drawBoard(g) ; 

} 

import javax.swing.* ; 
import java.awt.* ; 
import java.awt.event.* ; 

public class PBoard { 

    int startx, starty, width, height ; 
    int i, j ; 
    final int X_BOARD_POS = 200 ; 
    final int Y_BOARD_POS = 200 ; 
    final int SQUARE_SIZE = 50 ; 

    public PBoard() { 

    } 

    public void drawBoard(Graphics g) { 

    startx = X_BOARD_POS ; 
    starty = Y_BOARD_POS ; 
    width = SQUARE_SIZE ; 
    height = SQUARE_SIZE ; 

    for (i = 0; i<=7 ; i++){ 
     starty = Y_BOARD_POS ; 
     for (j = 0 ; j<= 7 ; j++){ 
     g.setColor(Color.gray) ; 
     g.fillRect(startx,starty,width,height) ; 
     g.setColor(Color.black) ; 
     g.drawRect(startx,starty,width,height) ; 
     starty = starty + SQUARE_SIZE ; 
     } 
     starty = X_BOARD_POS ; 
     startx = startx + SQUARE_SIZE ; 
    } 
    } 
} 

Answer 1

board是Connect靜態成員。由於MyDrawPanel不是Connect的子類，因此無法直接訪問它。使用Connect.board.drawBoard(g)而不是board.drawBoard(g)。